# Understanding Voltages in a circuit

#### Abhinavrajan

Joined Aug 7, 2016
83
Please look at the simple circuit and help me understand the concept of voltage.

1. Assume the circuit is in open condition. What would the voltage between point B and ground ? - Please answer this and help me understand a bit more clearly.

2. Assume the circuit is closed and current flows through it.

2a. What would be the value of voltage between point A and ground ?
2b. What would be the value of voltage between point B and ground ?

Please explain with some reason and in simple english. An example or analogy for the answers would be really great. Thanks.

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#### R!f@@

Joined Apr 2, 2009
9,786
With Switch closed.
A is across the battery so A to GND has Battery Voltage.
B is same as ground. So No voltage

And Switch open.
A and B has same voltage respective to GND as battery since no current is flowing through circuit.

#### AlbertHall

Joined Jun 4, 2014
12,026
1. With the switch open the voltage at both A & B will be 10V. A is simply the battery voltage. There is no current flowing so the voltage across the resistor is zero (V = I * R) and therefore the voltage at B is the same as A, 10V.
2a. The voltage at A is unchanged. It is the voltage across the battery.
2b. With the switch closed, B is connected directly to ground so there is zero voltage between B and ground. The difference between A & B is now equal to the battery voltage.
A the voltage at A
B the voltage at B
V voltage across the resistor
I current through the resistor
R the value of the resistor
V = I * R
I = V / R
I = (A - B) / R
I = (10V - 0V) / 10Ω
I = 10V / 10Ω
I = 1 amp.

#### Abhinavrajan

Joined Aug 7, 2016
83
With Switch closed.
A is across the battery so A to GND has Battery Voltage.
B is same as ground. So No voltage

And Switch open.
A and B has same voltage respective to GND as battery since no current is flowing through circuit.
Thank you!

#### Abhinavrajan

Joined Aug 7, 2016
83
1. With the switch open the voltage at both A & B will be 10V. A is simply the battery voltage. There is no current flowing so the voltage across the resistor is zero (V = I * R) and therefore the voltage at B is the same as A, 10V.
2a. The voltage at A is unchanged. It is the voltage across the battery.
2b. With the switch closed, B is connected directly to ground so there is zero voltage between B and ground. The difference between A & B is now equal to the battery voltage.
A the voltage at A
B the voltage at B
V voltage across the resistor
I current through the resistor
R the value of the resistor
V = I * R
I = V / R
I = (A - B) / R
I = (10V - 0V) / 10Ω
I = 10V / 10Ω
I = 1 amp.
Thank you!